Should accommodation be made for therapeutic delusion?

It seems to me that there are instances where beliefs can have a positive effect even when they are based on a questionable premise. An obvious example is the placebo effect: the belief that there is a valid scientific principle behind, say, a homeopathic medicine can be enough to provoke a very real physiological response that brings relief to the patient. The belief itself is delusional (from my point of view), but therapeutic. You could perhaps argue that the patient is better off for his delusion, and that to dispel that delusion would render him a disservice.

Then of course, there are cases where such a delusion would actually prevent a person from seeking a more effective, scientifically sound treatment that would bring even greater benefit. For that reason, it’s essential that doctors know the science, how the placebo effect works, and what the best alternatives are.

In many European countries, even mainstream doctors will routinely prescribe homeopathic medicines in case where there are no other clearly superior treatments. I suspect that the doctors don’t believe in the scientific basis of homeopathy, but they do know that the pills won’t have any side-effects, and often bring some real relief. Could it be then that the public at large is, on the whole, better off believing in this stuff?

But this is just an example. I would propose that there are other examples of therapeutic delusion, but I’ve already made you read too much. So, is the dispelling of delusion always an unqualified good? If allowances are made for therapeutic delusion in its various forms, how can it be kept in bounds?